[PATCH 2/4] dnp3: reduce flood threshold to 32 and make configurable

[PATCH 2/4] dnp3: reduce flood threshold to 32 and make configurable

Lower the number of unreplied requests from 500 to 32 to consider a
flood. At the very least this is an anomaly given the DNP3 spec mentions
that DNP3 should only have one outstanding request at a time, with an
exception for unsolicited responses, so in practice no more than 2
should be seen.

Additionally make this value configurable by introducing the max-tx
parameter.

Ticket: #8181
(cherry picked from commit a16f087b93be1ff2f2edf47371866ad9b28593c1)

Origin: upstream, https://github.com/OISF/suricata/commit/635af8dc8be09667689be71d781912718ca1aa49.patch
Bug: https://redmine.openinfosecfoundation.org/issues/8181
Subject: Upstream fix for CVE-2026-22259 part 2

Gbp-Pq: Name CVE-2026-22259_2.patch